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Species · California · BBS 2025 Release · 1966–2024

Black Oystercatcher Population Trend in California

All statesShorebirds

Black Oystercatcher in California has increased: up 44% on the route-weighted index since 1973.

+44%Since 1973TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
8Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
46YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black Oystercatcher Trends in CaliforniaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Black Oystercatcher in California. See the full index history below.

Black Oystercatcher Population Forecast in California

If the recent trend holds, Black Oystercatcher in California is projected to stay roughly flat through 2029, near 0.04 (95% range 0.00–0.08). A 5-year backtest shows a typical error of ±116.8%, with 80% of held-out values landing inside the 95% band.

n/aChange by 2029TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
0.04Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.0895% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±116.8%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Black Oystercatcher in California is projected to stay roughly flat through 2029, near 0.04 (95% range 0.00–0.08). A 5-year backtest shows a typical error of ±116.8%, with 80% of held-out values landing inside the 95% band.19682029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20250.040.000.08
20260.040.000.08
20270.040.000.08
20280.040.000.08
20290.040.000.08

Black Oystercatcher Survey Routes in California

Routes recording Black Oystercatcher in California.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Bodega Bay320211972
Crescent Cty219951974
Redwood N.P.220072007
Honeydew120171968
Harbor Lake 2120242015
Fish Rock120091973
Laytonville119901988
Morro Bay120121979

Black Oystercatcher Population Trend in Other States

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Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.